linux-kernel - Re: init's children list is long and slows reaping children.

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Message-ID: <4616CBF0.7090606@garzik.org>
Date:	Fri, 06 Apr 2007 18:38:40 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Robin Holt <holt@....com>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Jack Steiner <steiner@...ricas.sgi.com>
Subject: Re: init's children list is long and slows reaping children.

Robin Holt wrote:
> We have been testing a new larger configuration and we are seeing a very
> large scan time of init's tsk->children list.  In the cases we are seeing,
> there are numerous kernel processes created for each cpu (ie: events/0
> ... events/<big number>, xfslogd/0 ... xfslogd/<big number>).  These are
> all on the list ahead of the processes we are currently trying to reap.

What about attacking the explosion of kernel threads?

As CPU counts increase, the number of per-CPU kernel threads gets really 
ridiculous.

I would rather change the implementation under the hood to start per-CPU 
threads on demand, similar to a thread-pool implementation.

Boxes with $BigNum CPUs probably won't ever use half of those threads.

	Jeff



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